This invention relates to apparatus for the transmission of binary digital data which has been encoded in a code of the type known as the Miller Code.
The Miller Code represents the two binary states by a transition in the center of a bit period for one of the states and no transition there for the other. If two consecutive bit periods each have no transition in the center, then instead there is a transition between the two periods. Hereinafter a transition in the center of a bit period is assumed to represent a binary one and no transition a binary zero. An example of a code sequence is given in FIG. 1.
The code is inherently imbalanced and the random data frequency spectrum contains significant low frequency components which extend down to zero. The worst case imbalance occurs when transmitting a 1011011 pattern, and this is illustrated in FIG. 2. This imbalance is a significant disadvantage of the Miller Code in many applications, in particular when transformers need to be used.